Table 1.

Summary of reports on extra-articular synovial osteochondromatosis [13].

S No	Author/year	Age/Gender	Presentation	Radiology	Treatment	Biopsy
1	Franklin et al./1977	45/F	Recurrent swelling in anterior aspect of ankle	Radiograph - Irregularity in cortex of distal end of tibia and soft tissue swelling with calcification	Open exploration and excision	Lobules of cartilage within synovial tissue without bony invasion
2	Thomas et al./1980	47/F	Recurrent mass on the anterior aspect of the ankle	Radiograph - Soft tissue mass on anterior part of tibia with irregular margin and destruction of anterior cortex; Recurrence after 2 years - X ray revealed extensive lesion involving the anterior aspect of distal end tibia with intra - medullary extension	Subtotal excision biopsy Recurrence: B/K amputation	Initial HPE - Lobules of cartilage cells with intervening acellular stroma; HPE of recurrence - Two distinct patterns: 1) chondrocyte cluster with intervening acellular stroma, 2) sheets of cartilage cells with moderately atypical nuclei
3	Tibrewal et al./1995	44/F	Painful soft tissue mass over anterolateral aspect of right ankle	Radiograph - Lytic area in the lower tibia & fibula with scalloping of margin, extending to articular surface, soft tissue mass around ankle without calcification; CT - Well defined soft tissue mass with calcification and erosion of tibiofibular syndesmosis	Open excision	Lobules of cartilage with covering of hyaline material and synovium along with focal osteoid formation, some enlarged chondrocyte nuclei without atypia
4	Van et al./2006	56/F	Mass in the posterior aspect of left ankle for 2 years, pain for 6 months and increasing in size for 2 months	Radiograph - soft tissue density with a circumscribed mass posterior to ankle & subtalar joint; MRI - multiple cystic appearing masses along tibiotalar joint extending cephalad along the posterior margin of FHL. Anterior extension to talus through the sinus tarsi, laterally to anterior and medial margin of peroneal tendon, no ossification	Open excision	Chondrocyte metaplasia with cartilaginous nodules within synovial membrane
5	Kim et al./2013	32/M	Painful swelling left subtalar region laterally	Radiograph, CT - huge, rounded, finely stippled, calcified mass with radio-opaque bodies lateral to subtalar joint. MRI - T2 weighted high signal intensity compatible with calcification and ossification with hypointense septa	Open excision	Nodules of mature hyaline cartilage located under a layer of synovial membrane, with central ossification and osteoblastic rimming
6	Lui et al./2014	55/F	Lump over the dorsum of the foot with pain and gradually increasing size	MRI - Cyst around the EDL tendon with multiple calcified masses	EDL tendoscopy with synovectomy, ankle arthroscopy with removal of loose body & debridement	Cartilaginous nodules with inflamed synovial tissue
7	Nichelle et al./2015	17/F	Intermittent swelling and discomfort posterior to left medial malleolus	Radiograph - Soft-tissue density obscuring Kagers fat pad; MRI - distension of FHL tendon sheath with innumerable non ossified cartilage bodies measuring 1−4mm	open excision	Nodules rich in chondroid matrix with reactive chondrocytes
8	Pinter et al./2017	48/M	Painful mass over the posteromedial aspect of right ankle	Radiograph - Mass without calcification; MRI - 4 cm irregular mass involving FDL, FHL and PT	open excision	Cluster of clonal chondrocytes arranged in lobules, with variable atypia and occasional bi nucleation
9	Isbell et al./2017	27/M	Recurrence of progressively increasing left ankle pain and swelling along with tingling and burning in plantar aspect of foot	Radiograph - Opacity over the pre-Achilles fat pad and posterior ankle soft tissue; US - Joint capsule distension with intra articular debris and synovial hyperemia; MRI - Multiple large lobulated heterogeneous lesions with enhancement around FHL tendon extending into anterior tibiotalar joint and minimal involvement of sinus tarsi	Arthroscopic debridement of joint along with open excision	Cartilage hyaline nodules with minimal atypia of the chondrocytes and infrequent mitosis
10	Dheer et al./2020	49/F	Palpable swelling in the lateral aspect of ankle	US - Lobulated heterogeneous lesion with internal echogenicity; Doppler - neo vascularity; MRI - well lobulated mass near the peroneal tendon sheath with nodular and lace-like internal enhancement	Open surgical excision	Lobules of cartilage proliferation, minimal cellularity, no nuclear atypia and low nuclear to cytoplasmic ratio

Abbreviations: B/K – below knee, CT – computerized tomography, MRI – Magnetic resonance imaging, FHL – Flexor Hallucis Longus, EDL – Extensor Digitorum Longus, FDL – Flexor Digitorum Longus, PT – Tibialis Posterior US- Ultrasonogram, M – Male, F – Female.